Flexible alternating current (AC) transmission systems (FACTS) that utilize voltage-sourced inverters are increasingly used in power systems because of their improved performance when compared to conventional thyristor based systems. Two types of voltage sourced inverter that are used to provide compensation for non-linear and distorting loads are a Static Synchronous Compensator (STATCOM) and a Distribution STATCOM (D-STATCOM). In particular, the STATCOM and D-STATCOM systems are used at the power distribution level to compensate for harmonics that are introduced into the power distribution system due to the non-linear distorting loads.
Conventional STATCOM and D-STATCOM systems typically use active power filters to filter these harmonics. However, these active power filters reduce the power system performance due to the limited control bandwidth, delays in any digital implementation, and interactions with the non-linear distorting loads. In addition, in order to reduce the complexity of the D-STATCOM the pulse width modulation (PWM) switching frequency of a conventional D-STATCOM system may only be a few kilohertz. Thus, the bandwidth of the various control loops within the D-STATCOM is limited and this limited bandwidth reduces the ability of the D-STATCOM system to track and compensate for unwanted disturbances caused by the non-linear/distorting loads.
Therefore, it would be advantageous to provide a STATCOM and D-STATCOM system that uses a conventionally low PWM switching frequency and that is able to track and compensate for at least some disturbance harmonics generated by a non-linear distorting load.